The Chagos Archipelago (/ˈtʃɑːɡoʊs/ or /ˈtʃɑːɡəs/) or Chagos Islands (formerly the Bassas de Chagas,[1] and later the Oil Islands) is a group of seven atolls comprising more than 60 individual tropical islands in the Indian Ocean; situated some 500 kilometres (310 mi) due south of the Maldives archipelago. This chain of islands is the southernmost archipelago of the Chagos-Laccadive Ridge, a long submarine mountain range in the Indian Ocean.[2] The Chagos also form a terrestrial ecoregion together with the Maldives and the Lakshadweep.[3] The islands and their surrounding waters are also a vast oceanic Environment Preservation and Protection Zone (EPPZ) (Fisheries Conservation and Management Zone (FCMZ) of 544,000 square kilometres (210,000 sq mi)), an area twice the size of the UK's land surface.

Officially part of the British Indian Ocean Territory, the Chagos were home to the Chagossians for more than a century and a half until the United Kingdom evicted them in the early 1970s and allowed the United States to build a military base on Diego Garcia, the largest of the Chagos Islands. Since 1971, only the atoll of Diego Garcia is inhabited, and only by military and civilian contracted personnel.

The Chagos group is a combination of different coralline rock structures topping a submarine ridge running southwards across the centre of the Indian Ocean, formed by volcanoes above the Réunion hotspot. Unlike in the Maldives there is not a clearly discernible pattern of arrayed atolls, which makes the whole archipelago look somewhat chaotic. Most of the coralline structures of the Chagos are submerged reefs.

The Chagos contain the world's largest coral atoll (The Great Chagos Bank). It also has one of the healthiest reef systems in the cleanest waters in the world, supporting half the total area of good quality reefs in the Indian Ocean. As a result, the ecosystems of the Chagos have so far proven resilient to climate change and environmental disruptions.

On 1 April 2010, the British government Cabinet established the Chagos Archipelago as the world's largest marine reserve. At 640,000 km2, it is larger than the country of France or the state of California. It doubled the total area of environmental no take zones worldwide.[5] The protection of the marine reserve will be guaranteed for the next five years thanks to the financial support of the Bertarelli Foundation.[6] The setting up of the Marine Reserve would appear to be an attempt to prevent any resettlement by the evicted natives in the 1960s and 70s. Leaked US Cables have shown the FCO suggesting to the US counterparts that setting up a protected no-take zone would make it "difficult, if not impossible" for the islanders to return. The reserve was then created in 2010.[7]

Mauritius initiated on 20 December 2010 proceedings against the UK under the United Nations Convention on the Law of the Sea (UNCLOS) to challenge the legality of the MPA which the United Kingdom declared around the Chagos Archipelago.

On 18 March 2015, the Permanent Court of Arbitration unanimously held that the marine protected area (MPA) which the UK declared around the Chagos Archipelago in April 2010 violates international law. The Prime Minister of Mauritius pointed out that it is the first time that the UK's conduct with regard to the Chagos Archipelago has been considered and condemned by any international court or tribunal. He qualified the ruling as an important milestone in the relentless struggle, at the political, diplomatic and other levels, of successive Governments over the years for the effective exercise by Mauritius of its sovereignty over the Chagos Archipelago. The tribunal considered in detail the undertakings given by the United Kingdom to the Mauritian Ministers at the Lancaster House talks in September 1965. The UK had argued that those undertakings were not binding and had no status in international law. The Tribunal firmly rejected that argument, holding that those undertakings became a binding international agreement upon the independence of Mauritius, and have bound the UK ever since. It found that the UK's commitments towards Mauritius in relation to fishing rights and oil and mineral rights in the Chagos Archipelago are legally binding. The Tribunal also found that the United Kingdom’s undertaking to return the Chagos Archipelago to Mauritius when no longer needed for defence purposes is legally binding. This establishes that, in international law, Mauritius has real, firm and binding rights over the Chagos Archipelago, and that the United Kingdom must respect those rights. The Tribunal went on to hold that the United Kingdom had not respected Mauritius’ binding legal rights over the Chagos Archipelago. It considered the events from February 2009 to April 2010, during which time the MPA proposal came into being and was then imposed on Mauritius.[8][9]

The Chagos Archipelago.
(Atolls with areas of dry land are named in green)

The entire land area of the islands is a mere 56.13 km², with the largest island, Diego Garcia, having an area of 32.5 km². The total area, including lagoons within atolls, however, is more than 15,000 km², of which 12,642 km² are accounted by the Great Chagos Bank, the largest acknowledged atoll structure of the world (the completely submerged Saya de Malha Bank is larger, but its status as an atoll is uncertain). The shelf area is 20,607 km², and the Exclusive Economic Zone, which borders the corresponding zone of the Maldive Islands in the north, has an area of 639,611 km² (including territorial waters).

The number of atolls in the Chagos Archipelago is given as four or five in most sources, plus two island groups and two single islands, mainly because it is not recognized that the Great Chagos Bank is a huge atoll structure (including those two island groups and two single islands), and because it is not recognisd that Blenheim Reef has islets or cays above or just reaching the high-water mark.

In addition to the seven atolls with dry land reaching at least the high-water mark, there are nine reefs and banks, most of which can be considered permanently submerged atoll structures. They are listed in the table from north to south:

The deep oceanic waters around the Chagos Islands, out to the 200 nautical mile limit, include an exceptional diversity of undersea geological features (such as 6000 m deep trenches, oceanic ridges, and sea mounts). These areas almost certainly harbour many undiscovered and specially adapted species. Although the deepwater habitats surrounding the islands have not been explored or mapped in any detail, work elsewhere in the world has shown that high physical diversity of the sea floor is closely linked to a high diversity of species.

All economic activity is concentrated on the largest island of Diego Garcia, where joint UK-US military facilities are located. Construction projects and various services needed to support the military installations are done by military and contract employees from the UK, Mauritius, the Philippines, and the US. There are currently no industrial or agricultural activities on the islands. All the water, food and other essentials of daily life are shipped to the island. An independent feasibility study led to the conclusion that resettlement would be "costly and precarious". Another feasibility study, commissioned by organisations supporting resettlement, found that resettlement would be possible at a cost to the British taxpayer of £25 million. If the Chagossians return, they plan to re-establish copra production and fishing, and to begin the commercial development of the islands for tourism.

Until October 2010, Skipjack (Euthynnus pelamis) and yellowfin tuna (Thunnus albacares) were fished for about two months of the year as their year-long migratory route takes them through Chagos waters. While the remoteness of the Chagos offers some protection from extractive activities, legal and illegal fishing have had an impact. There is considerable poaching of turtles and other marine life. Sharks, which play a vital role in balancing the food web of tropical reefs, have suffered sharp declines from illegal fishing for their fins and as bycatch in legal fisheries. Sea cucumbers, which cleanse sand, are poached to feed Asian markets.

The Chagos Archipelago has a tropicaloceanic climate; hot and humid but moderated by trade winds. Climate is characterised by plenty of sunshine, warm temperatures, showers and light breezes. December through February is considered the rainy season (summer monsoon); typical weather conditions include light west-northwesterly winds and warmer temperatures with more rainfall. June to September is considered the drier season (winter), characterised by moderate south-easterly winds, slightly cooler temperatures and less rainfall. The annual mean rainfall is 2600 mm (100 inches), varying from 105 mm (4 inches) during August to 350 mm (14 inches) during January.

The Chagos had been part of Mauritius since the 18th century when the French first settled the islands. All of the islands forming part of the French colonial territory of Isle de France (as Mauritius was then known) were ceded to the British in 1810 under the Act of Capitulation signed between the two countries. In 1965, prior to Mauritian independence, the UK split the archipelago from the territory of Mauritius to form the British Indian Ocean Territory.[4]

United Nations' resolutions banned the dismemberment of colonial territories before independence. Mauritius has repeatedly asserted that the British claim that the Chagos Archipelago is one of its territories is a violation of law and of UN resolutions. The UK has stated that it has no doubt about its sovereignty over the Chagos but has also said that the Chagos will be returned to Mauritius once the islands are no longer required for defense purposes.[4]

According to Southern Maldivianoral tradition, local traders and fishermen were occasionally lost at sea and got stranded in one of the islands of the Chagos. Eventually they were rescued and brought back home.[11] However, these islands were judged to be too far away from the Maldives to be settled permanently by Maldivians. Thus for many centuries the Chagos were ignored by their northern neighbours.

In Maldivian lore the whole group is known as Fōlhavahi or Hollhavai (the latter name in the Southern Maldives Adduan dialect of Dhivehi). There are no separate names for the different atolls of the Chagos in the Maldivian oral tradition.[12]

Portuguese explorers were the first Europeans to discover the archipelago. Although Portuguese navigator Pedro de Mascarenhas (1470–June 23, 1555) is credited with having discovered the islands during his voyage of 1512–13, there is little corroborative evidence for this; cartographic analysis points to 1532 or later. Portuguese seafarers named the group as Bassas de Chagas,[13]Portuguese: Chagas (wounds) referring to the Holy Wounds of the crucifixion of Jesus. They named as well some of the atolls, such as Diego Garcia and Peros Banhos Atoll, mentioned as Pedro dos Banhos in 1513 by Afonso de Albuquerque.[14] Neglected by the Portuguese, this lonely and isolated group, economically and politically uninteresting, was never made part of the Portuguese Empire.[15]

The earliest and most interesting description of the Chagos, before coconut trees grew widely on the islands, was written by Manoel Rangel, a castaway from the Portuguese ship Conceição which ran aground on the Peros Banhos reefs in 1556.[16]

The French were the first to lay a claim on the Chagos after they settled Réunion (in 1665) and Isle de France (now Mauritius, in 1715). The French began issuing permits for companies to establish coconut oil plantations on the Chagos in the 1770s.[17]

On 27 April 1786 the Chagos Islands and Diego Garcia were claimed for Great Britain. However, the territory was ceded to Britain by treaty only after Napoleon's defeat, in 1814. The Chagos were governed from Mauritius, which was by that time also a British colony.[18]

In 1793, when the first successful colony was founded on Diego Garcia, the largest island, coconutplantations were established on many of the atolls and isolated islands of the archipelago. Initially the workers were slaves, but after 1840 they were freemen, many of whom were descended from those earlier slaves. They formed an inter-island culture called Ilois (a French Creole word meaning Islanders).

Commander Robert Moresby made a survey of the Chagos on behalf of the British Admiralty in 1838. After Moresby took measurements of most of the atolls and reefs, the archipelago was charted with relative accuracy for the first time.[19]

On 31 August 1903 the Chagos Archipelago was administratively separated from the Seychelles and attached to Mauritius.

In November 1965, the UK purchased the entire Chagos Archipelago from the then self-governing colony of Mauritius for £3 million to create the British Indian Ocean Territory (BIOT), with the intent of ultimately closing the plantations to provide the British territory from which the U.S. would conduct its military activities in the region. On 30 December 1966, the U.S. and the UK executed an Agreement through an Exchange of Notes which permit the United States Armed Forces to use any island of the BIOT for defense purposes for 50 years (through December 2016), followed by a 20-year optional extension (to 2036) to which both parties must agree by December 2014. As of 2010, only the atoll of Diego Garcia has been transformed into a military facility.

In April 1966 the British Government bought the entire assets and real property of the Seychellois Chagos Agalega Company, which owned all the islands of the BIOT, for £600,000 and administered them as a government enterprise while awaiting U.S. funding of its proposed facilities, with an interim objective of paying for the administrative expenses of the new territory. However, the plantations, both under their previous private ownership and under government administration, proved consistently unprofitable due to the introduction of new oils and lubricants in the international marketplace, and the establishment of vast coconut plantations in the East Indies and the Philippines.

Between 1967 and 1973, the entire population was removed against its will from the islands and relocated to Mauritius and the Seychelles to make way for a joint United States-United Kingdom military base on Diego Garcia.[20] In March 1971, Seabee U.S. Naval construction battalions arrived on Diego Garcia to begin the construction of the Communications Station and an airfield. To satisfy the terms of an agreement between the UK and the U.S. for an uninhabited island, the plantation on Diego Garcia was closed in October of that year. The plantation workers and their families were initially relocated to the plantations on Peros Banhos and Salomon atolls in the northwest of the archipelago; those who requested were transported to the Seychelles or Mauritius. In 1972, the UK decided to close all the remaining plantations throughout the Chagos, and deported the Ilois to the Seychelles or Mauritius. The then-independent Mauritian government refused to accept the islanders without payment, and in 1973, the UK gave the Mauritian government an additional ₤650,000 to resettle the islanders. However, despite this islanders often found themselves in woefully inadequate housing and living conditions.

Currently, the only human structures on the islands are located in the joint defence and Naval Support Facility Diego Garcia. Other uninhabited islands, especially in the Salomon Atoll, are common stopping points for long-distance yachtsmen traveling from Southeast Asia to the Red Sea or the coast of Africa, although a permit is required to visit the outer islands.

There are no indigenous peoples living on the island, and the UK represents the Territory internationally. A local government as normally envisioned does not exist.[21] Around 1,700 military personnel and 1,500 civilian contractors, mostly American, are stationed on Diego Garcia.[22]

There are two transnational political issues which affect the BIOT, through the British government.

First, the island nation of Mauritius claims the Chagos Archipelago (which is coterminous with the BIOT), including Diego Garcia. A subsidiary issue is the Mauritian opposition to the 1 April 2010 UK Government's declaration that the BIOT is a Marine Protected Area with fishing and extractive industry (including oil and gas exploration) prohibited.[23]

Second, the issue of compensation and repatriation of the former inhabitants of several of the archipelago's atolls, exiled since 1973, continues in litigation and as of 23 August 2010[update] has been submitted to the European Court of Human Rights by a group of former residents.[24]

Litigation continues as of 2012 regarding the right of return for the displaced islanders and Mauritian sovereignty claims. In addition, advocacy on the Chagossians' behalf continues both in the United States and in Europe.[25]

According to Wikileaks CableGate documents,[26] the UK proposed in 2009 that the BIOT become a "marine reserve". The summary paragraph of the referenced diplomatic cable follows:

"HMG would like to establish a marine park or reserve providing comprehensive environmental protection to the reefs and waters of the British Indian Ocean Territory (BIOT), a senior Foreign and Commonwealth Office (FCO) official informed Polcouns on May 12. The official insisted that the establishment of a marine park—the world's largest—would in no way impinge on USG use of the BIOT, including Diego Garcia, for military purposes. He agreed that the UK and U.S. should carefully negotiate the details of the marine reserve to assure that U.S. interests were safeguarded and the strategic value of BIOT was upheld. He said that the BIOT's former inhabitants would find it difficult, if not impossible, to pursue their claim for resettlement on the islands if the entire Chagos Archipelago were a marine reserve."[27]

The islanders were known as the Ilois (one French Creole word for "islanders") and they numbered about 1,000. They were of mixed African, South Indian, and Malay descent and lived very simple, spartan lives in their isolated archipelago. Few remains of their culture have been left, although their language is still spoken by some of their descendants in Mauritius and the UK.

The inhabitants of Chagos were speaking Chagossian Creole, also known as Ilois creole, a FrenchCreole which has not been properly researched from the linguistic point of view.

The biodiversity of the Chagos archipelago and its surrounding waters is one of the main reasons it is so special. But this incredible diversity is under threat as at least 60 species that call Chagos home are already on the IUCN Red List of Threatened Species.[citation needed]

The reefs host at least 371 species of coral including the endemicbrain coralCtenella chagius. The coral cover is dense and healthy even in deep water on the steep outer reef slopes. Thick stands of branching staghorn coral (Acropora sp) protect the low lying islands from wave erosion. Despite the loss of much of the coral in a bleaching event in 1998 the recovery in the Chagos has been remarkable and overall coral cover increases year on year.[citation needed]

Fish

The reefs are also home to at least 784 species of fish that stay near to the shores of the islands including the endemic Chagos clownfish (Amphiprion chagosensis) and many of the larger wrasse and grouper that have already been lost from over-fishing in other reefs in the region.[citation needed]

As well as the healthy communities of reef fish there are significant populations of pelagic fish such as manta rays (Manta birostris), sharks and tuna. Shark numbers have dramatically declined as a result of illegal fishing boats that seek to remove their fins and also as accidental by-catch in the two tuna fisheries that used to operate seasonally in the Chagos.[citation needed]

Coconut crabs are the world's largest terrestrial arthropod and live in one of the most undisturbed populations in the Chagos

The coconut crab (Birgus latro) is the world's largest terrestrial arthropod, reaching over one metre in leg span and 3.5-4 kilos in weight. As a juvenile it behaves like a hermit crab and uses empty coconut shells as protection but as an adult this giant crab climbs trees and can crack through a coconut with its massive claws. Despite its wide global distribution, it is rare in most of the areas it is found. It is primarily threatened by over-collection for food, but also as ornaments for sale to tourists and as bait for fish traps. Demand for coconut crabs as souvenirs is strong, and other threats include habitat destruction and predation from introduced species such as rats. The coconut crabs on Chagos constitute one of the most undisturbed populations in the world. An important part of their biology is the long distances their young can travel as larvae. This means the Chagos coconut crabs are a vital source for replenishing other over-exploited populations in the Indian Ocean region.[citation needed]

A total of 113 species of insect have been recorded from the Chagos Islands.[citation needed]

Plants

The Chagos Islands have been colonised by plants since there was sufficient soil to support them – probably less than 4,000 years. Seeds and spores arrived on the emerging islands by wind and sea, or from passing sea birds. The native flora of the Chagos Islands is thought to comprise forty-one species of flowering plants and four ferns as well as a wide variety of mosses, liverworts, fungi and cyanobacteria.[citation needed]

Today, the status of the Chagos Islands’ native flora depends very much on past exploitation of particular islands. About 280 species of flowering plants and ferns have now been recorded on the islands, but this increase reflects the introduction of non-native plants by humans, either accidentally or deliberately. Because some of these non-native species have become invasive and pose a threat to the native ecosystems, plans are being developed to control them. On some islands, native forests were felled to plant coconut palms for the production of copra oil. Other islands remain unspoiled and support a wide range of habitats, including unique Pisonia forests and large clumps of the gigantic fish poison tree (Barringtonia asiatica). Unspoiled islands provide us with the biological information that we need in order to re-establish the native plant communities on heavily altered islands. These efforts will ultimately help to improve the biodiversity of the Chagos Islands.[citation needed]

The Chagos is one of the few marine locations in the world where there are almost no ongoing, direct human impacts over almost all of its areas. In April 2010 the Chagos was designated as a marine reserve by the UK government. That will, among other things, allow the area to serve as a reference site for global scientific research to aid in understanding of such things as climate change, tropical marine ecosystems and the impacts of commercial fisheries.

This followed an effort led by The Chagos Environment Network,[33] a collaboration of nine leading conservation and scientific organisations seeking to protect the rich biodiversity of the Chagos Archipelago and its surrounding waters. The Chagos Environment Network cites several reasons for supporting a protected area:

Wildlife

The Chagos no-take marine reserve would maintain the pure and unpolluted waters of Chagos, providing a safe refuge for its rich marine life, including many threatened animals, such as turtles and sharks. Seabirds and nesting turtles too will benefit from the additional conservation measures that a protected area will bring. Both groups are recovering from severe depredations of the past in a way that is not possible in most places.

Fisheries

World fish stocks have declined because the human race exploits the sea. A large ‘no-take’ protected area will assist fish population recovery, potentially increasing fish numbers over a much wider area. The protected area will also provide a temporary refuge for migratory species, such as tuna, from exploitation. However, there have been arguments for keeping a controlled fishery, the fees from which could be used to support conservation efforts in the area.

People

With regard to the forcibly removed Chagossian people, whatever the outcome of legal challenges brought by Chagossian groups against the UK government, the Chagos Environment Network believes that the Chagos Archipelago need conservation now and that this will be beneficial to everyone under all future legal scenarios. The Chagos Environment Network urged that the Chagos Islands and their surrounding waters be designated as a no-take marine reserve "without prejudice” to the outcome of the legal process. This designation would mean that the Chagos Islands and their resources would remain healthy no matter what the future holds, but that conservation arrangements could be modified if necessary in the light of a change in circumstances.

Science

The Chagos is one of the few marine locations in the world where there are almost no ongoing, direct human impacts over almost all of its areas (with the obvious exception of the huge military base on the main island). The marine reserve could serve as a reference site for global scientific research to aid in our understanding of such things as climate change, tropical marine ecosystems and the impacts of commercial fisheries.

Deep ocean

The deep oceanic waters around the Chagos Islands, out to the 200 nautical mile limit, include an exceptional diversity of undersea geological features (such as 6000m deep trenches, oceanic ridges and sea mounts). These areas almost certainly harbour many undiscovered and specially adapted species.

UK international commitments

The creation of the Chagos Protected Area would be an important contribution by the UK to at least seven international environmental conventions. It would also contribute to the UK’s global commitments, such as halting the decline of biodiversity by 2010, establishing marine protection networks by 2012, and restoring depleted fish stocks to sustainable levels by 2015.

The UK government opened a three-month public consultation which ended after the 5th of March 2010 about conservation management of the Chagos Islands and its surrounding waters.[34]